Transmission of short, strong thermal pulses through liquid helium
Iznankin A.Yu., Mezhov-Deglin L.P.
The relaxation of pulse perturbations in liquid helium was investigated. The width of the recorded pulses of the second sound increases with increasing amplitude of the ~ l-//sec exciting thermal pulse; at T< 1.87 К the leading edge of the pulse is shifted and at T> 1.87 the pulse decreases while its leading edge remains almost stationary. At Τλ — T< 0.2 К and T> Τλ +0.2 К the propagation of the pulses of the first sound can be recorded. The arrival in the receiver of the pulse of the first sound in He II corresponds to a decrease of the temperature and its arrival in He I corresponds to an increase in the temperature, i.e., in both cases a compression wave propagates from the heater in the liquid.